1. Field of the Invention
The present invention relates to a setting tool for driving nail-shaped attachment elements into a hard structural component, and including a housing, a guide cylinder located in the housing, a drive piston axially displaceable in the guide cylinder and having a driving surface, a lever-shaped resetting member pivotable in a plane extending parallel to a setting direction, an axle for supporting the resetting member for pivotal movement, and a spring for biasing the resetting member toward the driving surface of the drive piston.
2. Description of the Prior Art
At present, explosive powder charge-operated setting tools are used for driving nail-shaped attachment elements into hard structural components, e.g., concrete, rock or steel. These setting tools have a housing, a guide cylinder at least partially located in the housing, a drive piston axially displaceable in the guide cylinder and acting directly on the attachment element during the drive-in process. After each drive-in step, the drive piston should be return into its initial position.
German Publication DE-OS 18 12 207 discloses a setting tool in which the drive piston is returned into its initial position with a lever-shaped, spring-biased resetting member pivotable relative to the setting tool housing in a plane extending in a setting direction. The resetting member projects through a side opening formed in the guide cylinder into the interior of the guide cylinder and cooperates there with the driving surface of the drive piston. The resetting member pivots about a rotational axle supported in the setting tool housing. The biasing spring is supported, on one hand, against the housing and, on the other hand, against the resetting member. The biasing spring becomes preloaded upon displacement of the drive piston in the setting direction. After the completion of a setting process, the spring is relaxed, providing for pivoting of the resetting member in a direction opposite to the setting direction until the drive piston is returned to its initial position.
The drive piston of the above-discussed German Publication has adjacent guide and seal regions, with the guide region facing in the setting direction. The diameter of the seal region substantially corresponds to the diameter of the guide cylinder, and the diameter of the guide region substantially corresponds to the diameter of a guide bore formed in the housing of the setting tool. The guide region of the drive piston is subject to wear, so that the drive piston should be replaced from time to time. In the disclosed setting tool, the replacement of the drive piston is an extremely difficult and time-consuming process. This is because the resetting member, which entirely projects into the guide cylinder, should be dismounted from the housing in order to be able to unscrew the guide cylinder which is connected with the housing by a thread connection.
Accordingly, an object of the present invention is a setting tool which would insure a rapid and simple replacement of the drive piston.